1. Field
The present disclosure relates generally to aircraft and, in particular, to testing aircraft. Still more particularly, the present disclosure relates to a method and apparatus for testing aircraft in which an engine ceases to operate.
2. Background
In designing and certifying aircraft, various types of testing are performed. The tests are performed to determine whether an aircraft meets different types of performance standards. These standards may relate to safety, air pollution, noise, passenger comfort, and other suitable types of standards. Based on the results of the testing, an aircraft may change in design. In other cases, procedures on operating aircraft may be developed based on the tests. For example, different procedures may be identified for operating an aircraft under different conditions. These conditions may include weather, status of the equipment in aircraft, and other conditions.
For example, one test that may be performed on an aircraft involves identifying a minimum controllability speed for the aircraft. This speed is identified for aircraft in the event that one of the engines of the aircraft ceases to operate while the aircraft is moving on the ground during a takeoff phase of flight.
With this test, the operation of the engine is cutoff at different speeds while the aircraft is accelerating with maximum thrust applied for takeoff. These speeds are referred to as cutoff speeds. The operation of the engine is cutoff by a pilot moving a fuel control switch to a cutoff position. When the fuel control switch moves to the cutoff position, the fuel to one engine of the aircraft is cutoff. As a result, the engine stops operating.
The pilot attempts to move the fuel control switch to the cutoff position as close as possible to the time at which a cutoff speed is reached for the test such that the engine operation ceases about when the aircraft reaches the cutoff speed. When the operation of the engine ceases, lateral deviation occurs for the aircraft, which is controlled by the pilot using directional control inputs.
Data is gathered about the performance of the aircraft in response to the engine ceasing operation. One piece of data is the amount of lateral deviation. This lateral deviation towards the edge of the runway is a strong function of the cutoff speed.
The cutoff speed may be selected for the initial test in which the lateral deviation is expected to be less than 30 feet. Subsequent tests may involve successively reducing the cutoff speed until a lateral deviation of at least 30 feet is obtained.
In this manner, a minimum controllability speed at which a decision point may be made as to whether to halt a takeoff or continue with a takeoff in the event that an engine ceases operating is identified. If minimum controllability speed is not exceeded, that takeoff is aborted in this example.
Moving the fuel control switch to the cutoff position at the cutoff speed selected for the test requires concentration and good dexterity. The pilot anticipates when the speed selected for the test will be reached and moves the fuel control switch such that the cutoff position occurs as close to the selected speed as possible.
Moving the fuel control switch to the cutoff position when the selected speed is reached is a difficult operation to perform. Often times, the speed may be too low or too high. As a result, the undesired result of departing the side of the runway is greatly increased. In addition, the test may be repeated in an attempt to collect data for the desired speed.
These additional tests may increase the wear and tear on the engine and other portions of the aircraft. As a result, maintenance may be required sooner and more often than desired. Furthermore, repeat test points require the use of additional fuel and time on a runway. In some cases, the data collected may not be as consistent as desired based on the ability of the pilot to move the fuel control switch to the cutoff position at the selected speed for the test.
Therefore, it would be desirable to have a method and apparatus that take into account at least one of the issues discussed above as well as possible other issues. For example, it would be desirable to have a method and apparatus that increases the accuracy and reduces the effort needed to test an aircraft to obtain information for identifying a minimum controllability speed for the aircraft.